The statement "Even as a bird carries food to its nestlings till they are fledged, and never ceases to work for them, while she is herself but ill fed, so has it been with me" uses figurative language to express Achilles' feelings of sacrifice and unreciprocated effort. He compares himself to a mother bird who tirelessly works to provide for her young, even at the cost of her own well-being. This suggests that Achilles has dedicated himself to fighting for King Agamemnon and the Greek army, putting himself in danger and neglecting his own needs, yet feels he has not been properly recognized or rewarded for those sacrifices.
Therefore, the best response that captures this meaning is:
Achilles feels as though he has done a great deal for King Agamemnon and has been treated poorly in return.